tests: Expect the 192b ECDSA tests to fail in fips mode

* tests/dsa-rfc6979.c (check_dsa_rfc6979): Expect ECDSA 192b keys to
  fail in FIPS mode.
  (main): Detect FIPS mode.

The 192b ECDSA curve is not FIPS approved so it does not work. This adds
a flag to the list of the keys to mark if it is expected to work in FIPS
mode.

• Signed-off-by: Jakub Jelen <jjelen@redhat.com>